Testicular microvascularization in the common tree shrew (Tupaia glis) as revealed by vascular corrosion cast/SEM and by TEM.

Testicular angioarchitecture in lower primates has not been established and the route of androgens from Leydig cells entering the systemic circulation is still a matter of controversy. In the present study, the common tree shrew (Tupaia glis) was used as the model for vascular corrosion cast/SEM and conventional TEM studies. With vascular corrosion cast/SEM, it was revealed that while coursing in the spermatic cord, the testicular artery convoluted and gave off branches to supply the epididymis, the coverings of the spermatic cord and the pampiniform plexus. Upon approaching the testis, it encircled the organ, then penetrated into the testicular parenchyma near the rostro-medial pole before further dividing into arterioles that gave rise to capillary plexuses looping around the seminiferous tubules. These capillaries converged into the intratesticular venules, then into larger venules on ventral and dorsal surfaces of the testis and finally into the collecting veins on medial and lateral borders of the testis. In addition, the capillaries in the central or medullary portion of the gland collected the blood into the medullary venules and central (medullary) vein, respectively. The collecting veins as well as central vein joined together before dividing into pampiniform plexus. With transmission electron microscopy, the capillaries in the testis were shown to be of the thick basement membrane and continuous type. The Leydig cells were found adjacent to lymphatic vessels among the seminiferous tubules. This structure is compatible with the idea that most of the androgens drain into the lymphatic vessels rather than into the capillaries.

Microvascularization in trigeminal ganglion of the common tree shrew (Tupaia glis).

Since there is only a limited number of studies of the blood supply to the trigeminal ganglion (TG) in mammalian species, the TG from 16 common tree shrews (Tupaia glis) were investigated by light microscope, transmission electron microscope (TEM) and the corrosion cast technique in conjunction with scanning electron microscope (SEM). It was found that the TG contained clusters of neurons in the peripheral region whereas the bundles of nerve fibers were located more centrally. Each ganglionic neuron had a concentric nucleus and was ensheathed by satellite cells. It was noted that blood vessels of a continuous type were predominantly found in the area where the neurons were densely located and were much less frequently observed in the area occupied by nerve fibers. With TEM, the TG was shown to be mainly associated with large neurons containing big nuclei and prominent nucleoli. The blood supply of the TG is derived from the most rostral branch of the pontine artery, from the stapedial artery or sometimes from the supraorbital artery, and from the accessory meningeal artery which is a branch of the maxillary artery passing through the foramen ovale. These arteries give off branches and become capillary networks in the ganglion before draining blood to the peripheral region. The veins at the medial border drained into the cavernous sinus directly or through the inferior hypophyseal vein, while those at the lateral side of the ganglion carried the blood into the pterygoid plexus via an accessory meningeal vein. The veins along the trigeminal nerve root joined the posterior part of the cavernous sinus. These studies establish a unique anatomical distribution of the TG blood supply in the tree shrew and the utility of the cast/SEM technique in discerning detailed features of the blood supply in the nervous system.